Method of making phonograph records



May 23, 1933.

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INVENT Charles 6. Has/h Patented May 23, I933 UNITED STATES PATENT OFFICE CHARLES C. I'IASIN, OF LYNBROOK, NEW YORK, .ASSIGNOR TO ELECTRO BROADCASTERS CORPORATION, OF NEW YORK, N. 'Y., A CORPORATION OF NEW YORK METHOD OF MAKING IHONOGRAPH RECORDS Application. filed October 10, 1930. Serial No. 487,719.

This invention. relates to the manufacture of phonograph records, and has forits principal object to provide records having the record grooves thereof more closely spaced than has heretofore been practicable, whereby a longer program than heretofore may be recorded on a record of given size. The advantages of the results thus produced in the reduction of cost of production, re

duction of storage space required, and saving in handling and'shipping are obvious. The advantage is particularly pronounced in the case of records made for use with talking motion pictures, since the entire sound record for a picture may be made on fewer or smaller records than heretofore.

A pronounced limitation upon the compactness of records as heretofore made has lain in the fact that the surface of the master record or mold fromivhich commercial records are produced has been of too weak, or of too uneven composition to permit reduction in the wall thickness between adjacent cuts or grooves from that which has been maintained as standard practice. The weakness of the surface and the uncertainty of composition resulting from lack of homogeneity has made it necessary to allow between adjacent grooves sufficient space to provide ample wall strength even where weak portions of the record mold are encountered. i

Itis an object of the present invention to strengthen the surface of the master record, to render the surface uniform, and to render the master record material homogeneous for a sufiicientdeptlnat least, to make sure that no equalities will exist to r the maximum depth of the record grooves to 4 be out. Advantage is further taken of this improvement in the record mold material by adjusting the recording mechanism to inscribe the grooves closer together than. heretofore, and by employing a. cutting stylus which is more sharp-pointed than those heretofore employed. The increased sharpness of the stylus provides a groove with steeper side walls than heretofore. By cutting the grooves narrower and at the same time placing them closer together, I

have found it practicable to increase the line density of 80 to 100 lines per-inch,

which is customary in prior commercial practice, to at least 140 to 200 lines per Figure 1 is a diagrammatic view illus trating a master record and a stylus acting thereon to cut a spiral record groove;

Figure 2 is a fragmentary, sectional view on a much larger scale than Figure 1 taken on the line 22 of Figure 1 and looking in the direction of the arrows;

Figure 3 is a fragmentary, front elevation of the cutting stylus employed; and

Figure 4 is a fragmentary, side elevation of'the cutting stylus.

A master record or mold 1 is illustrated in Figure 1 in the process of having a record groove cut in it by a stylus 2.

The master record 1 is in the form of a thick wax disc. The composition of the disc may vary widely, but I have secured very good results with a disc having substantially the following composition:

Montan wax; 25% Stearic acid; 50% Lead oxide 20% Sodium carbonate Discs composed of the materials stated above have heretofore been used for master records. In accordance with the present invention, however, the homogeneity and strength of the disc is greatly lmproved by treatment preliminary to the cutting of the record. Such treatment may consist, for' example, of the following steps:

l Vhen the master record has thus been.

prepared, the recording apparatus is set to inscribe the record upon it at a line density of 140 to 200 lines per inch and the record is made at once without permitting the master record blank to cool to room temperature. In inscribing the record a sapphire pointed stylus 2 is employed having the side edges of the cutting tip thereof disposed at an angle of about 76 to one another, as contrusted with the usual angle of about 87. It will be apparent, of course, that the groove cut by this stylus will be considerably narrower and will have steeper pitched walls than grooves cut in accordance with. the hitherto known commercial practice. It is obvious, also, that less space is permitted to intervene between adjacent grooves than has heretofore been customary. The cutting of narrower grooves and the closer spacing of the grooves is made practicable by the increased strength of the 'wall material left between the grooves and by the fact that the record is out while the record blank is warm. If, without previous heat treatment of the blank, the cutting at the line density referred to should be attempted, the lines would run into one another. If cut at or below room temperature, after the heat treatment referred to, chipping would result.

When the cutting of the record by the stylus is complete, the master record is allowed to cool and is employed as a mold for the production of commercial records in the usual manner.

While I have illustrated and described in detail one embodiment of the invention, it is to be understood that changes may be made therein. I do not, therefore, desire to limit myself to the specific construction illustrated but intend to cover my invention broadly in whatever form its principles may be utilized.

I claim: l. The method of making phonograph records, which comprises providing a master record blank from which the commercial records are to be made, repeatedly heating the blank to strengthen it and render it homogeneous, and cutting a record-groove on the blank having a line density of 140 or more lines per inch.

2. The method of making phonograph records, which comprises providing a waxy master record blank from which the commercial records are to be made, heating the blank to a: temperature substantially above normal room temperature and maintaining it at such temperature for a considerable period, cooling the blank to a temperature below normal room temperature and maintaining. itat such temperature for a considerable period, again heating the blank above normal room temperature and maintaining it at such temperature for a considerable period, facing off the blank, and cutting a record groove of high line density upon the blank.

3.. The method of making phonograph records, which comprises providing a master record blank from which the commercial records are to be made, the blank having substantially the following composition: Montan wax 25%, stearic acid 50%, lead 0X- ide 20%, sodium carbonate 5%, heating the blank to a temperature substantially above normal room temperature and maintaining it at such temperature for a considerable period, cooling the blank to a temperature below normal room temperature and main-a.

taining it at such temperature for a considerable period, again heating the blank above normal room temperature and maintaining it at such temperature for a considerable periochfacing oif the blank, and cutting a record groove of high line density upon the blank.

4. The method of preparing a waxy master record blank for receiving a record of high line density, which comprises heatingthe blank to a temperature substantially above room temperature, maintaining it at such temperature for about a day, facing off the surface of the blank, cooling the blank to a temperature below room temperature,

- maintaining it at such temperature for about a day, again heating the blank to a temperature above room temperature, maintaining itat such temperature for about a day, and facing off the blank. 7

5. The method of preparing a waxy master record blank for receiving a record of high line density, which comprises heating the blank to a temperature of about 90 F., maintaining it at such temperature for about a day, cooling the blank to a temperature of about 65 F., maintaining it at such temperature for about a day, heating the blank to a temperature of about 80 F., maintaining it at such temperature for about a day, and facing off the blank.

In testimony whereof I have aflixed my signature to this specification.

CHARLES C. HASIN. 

